I went on the 7-day Caribbean cruise that summer. We went to Cozumel, Grand Cayman, and Jamaica. I spent lots of time sweating and in the water with no troubles! I sweated the day out at Chitzen Itza, got in saltwater at Stingray City, climbed Dunn's River Falls, and spent time at the beach. My only leak happened on the trip to Galveston (car rides tend to cause leaks for me sometimes due to sitting with the seatbelt and position of body/clothing). On the trip, I changed my bag twice on the cruise. I did it at night before bed so everything had time to dry in position before the next day's activities. I changed after the saltwater because I wanted to avoid any trouble the next day in Jamaica due to it just being difficult to change.
Also, I've been to the beach two other times this summer with no troubles. I do wear a wrap under my swimsuit (as I do every day under my regular clothes). The swim wrap is for swimming and dries quickly. It's from ostomysecrets.
I hope this helps! Have fun on your trip!